1,720,973 research outputs found
Neuromodulation for the treatment of drug-resistant epilepsy
No full textStereotactic radiosurgery provides a safe nonresective option to treat medically refractory epilepsy. The radiosurgical ablation of an epileptic focus, especially when performed through frameless image-guided radiosurgery, is a thoroughly noninvasive treatment devoid of the risks of open surgical procedures. Radiosurgery can be offered to patients harboring neocortical, hippocampal, or diencephalic seizure foci not requiring invasive mapping. Disconnective procedures such as radiosurgical callosotomy can be performed as well. This chapter will review the state of the art of radiosurgery for epilepsy, with special emphasis placed on robotic image-guided frameless delivery
Trigeminal Neuralgia
No full textTrigeminal Neuralgia (TN) is the most common cranio-facial pain syndrome, with an incidence of up to 5 in 100,000. Long-term medical treatment is commonly required, with up to 10% of cases suffering adverse drug-related events. In 1951, Lars Leksell pioneered the application of stereotactic irradiation for the treatment of TN, which may now achieve up to 90% pain control at 1 year and 60% at 3-5 years.
Radiosurgical treatment targets either the nerve’s emergence (the root entry zone) or the retrogasserian portion of the nerve (pars triangularis). Targeting the latter may reduce the risk of complications, but requires a higher maximum dose to obtain optimal results. Generally speaking, radiosurgical treatment achieves optimal results in patients receiving high doses of radiations ranging from 70 to 90 Gy. Hypoesthesia and facial numbness are frequently observed after high-dose trigeminal irradiation. Mild hypoesthesia is acceptable and is considered by many an efficacy endpoint of the procedure. Bothersome facial numbness is relatively rare. Sensitive trigeminal disturbances and paresthesia after treatment have been reported to range respectively 6%–54% and 0%–17%. The prescribed dose and brainstem-delivered dose are correlated with the subsequent rate of sensitive trigeminal disturbances. CyberKnife frameless non-isocentric radiosurgery is an emerging and non-invasive treatment for TN. Because of the non-isocentric geometry of radiation beams delivery, CyberKnife technique offers the possibility of homogeneous irradiation of an extended segment of the trigeminal nerve, so introducing some new concepts for the radiosurgical treatment of TN. Clinical results of CyberKnife radiosurgery seems to be satisfactory. We here review the basics of radiosurgery for TN and present a detailed analysis of the technique using the CyberKnife frameless system
Image-Guided Stereotactic Radiosurgery for Optic Nerve Sheath Meningiomas
No full textOptic nerve sheath meningiomas (ONSMs) are benign lesions primarily originating from the dural sheath of the optic nerve. Their progressive growth can lead to gradual loss of vision and exophthalmos. Treatment of these lesions is problematic and depends on the degree of visual impairment and proptosis. In patients with preserved vision and no proptosis, conservative management with frequent ophthalmologic and radiological follow-up is usually preferred. When vision begins to fail surgical intervention can be attempted, but it is often of limited success as far as preserving vision is concerned.
Radiotherapy has gained an increasing role in the management of these lesions. Conventional radiotherapy has been used both pre-operatively and post-operatively for many years. More recently fractionated stereotactic radiotherapy has been employed as an alternative to surgery, and may be superior in terms of vision preservation. Care must be however exercised due to the proximity of other important radiosensitive structures. Highly conformal treatments modality, such as those provided by radiosurgery, may overcome this issue. Frame-based stereotactic radiosurgery has been rarely used because single-fraction high-dose irradiation of the optic nerve may be associated with loss of vision. New frameless radiosurgery devices, such as the robotic CyberKnife, an image-guided radiosurgery system, can provide the extremely tight conformality and submillimetric accuracy of frame-based systems combined with the possibility of delivering radiation in multiple sessions. Here, the authors review the clinical presentation and management of ONSMs, highlighting the emerging use of hypofractionated radiosurgery to treat these challenging lesions
Image-guided LINAC radiosurgery in hypothalamic hamartomas
Full text linkINTRODUCTION: Hypothalamic hamartomas (HH) are developmental malformations that are associated with mild to severe drug-refractory epilepsy. Stereotactic radiosurgery (SRS) is an emerging non-invasive option for the treatment of small and medium-sized HH, providing good seizure outcomes without neurological complications. Here, we report our experience treating HH with frameless LINAC SRS. MATERIALS AND METHODS: We retrospectively collected clinical and neuroradiological data of ten subjects with HH-related epilepsy that underwent frameless image-guided SRS. RESULTS: All patients underwent single-fraction SRS using a mean prescribed dose of 16.27 Gy (range 16–18 Gy). The median prescription isodose was 79% (range 65–81 Gy). The mean target volume was 0.64 cc (range 0.26–1.16 cc). Eight patients experienced complete or near complete seizure freedom (Engel class I and II). Five patients achieved complete seizure control within 4 to 18 months after the treatment. Four patients achieved Engel class II outcome, with stable results. One patient had a reduction of seizure burden superior to 50% (Engel class III). One patient had no benefit at all (Engel class IV) and refused further treatments. Overall, at the last follow-up, three patients experience class I, five class II, one class III and one class IV outcome. No neurological complications were reported. CONCLUSIONS: Frameless LINAC SRS provides good seizure and long-term neuropsychosocial outcome, without the risks of neurological complications inherently associated with microsurgical resection
Cyberknife Radiosurgery for Trigeminal Neuralgia
Full text linkIntroductionImage-guided robotic radiosurgery is an emerging minimally-invasive treatment option for trigeminal neuralgia (TN). Our group has treated 560 cases up to date, and report here the clinical outcomes of 387 treatments with three years follow-up. This study represents the largest single-center experience on CyberKnife radiosurgery for the treatment of TN so far reported.MethodsCyberKnife radiosurgery treatment was offered to patients with drug-resistant TN, after the failure of other treatments or refusal of invasive procedures. A second treatment was offered to patients with a poor response after the first treatment or with recurrent pain. Treatment protocol required the non-isocentric delivery of 60 Gy prescribed to the 80% isodose to a 6 mm retrogasserian segment of the affected trigeminal nerve. Retreatments typically received 45 Gy, again prescribed to the 80% isodose. The final plan was developed accordingly to individual anatomy and dose distribution over the trigeminal nerve, gasserian ganglion, and brainstem. Clinical outcomes such as pain control and hypoesthesia/numbness have been evaluated after 6, 12, 24, and 36 months.ResultsOur group has treated 527 patients with Cyberknife radiosurgery at Centro Diagnostico Italiano (CDI), Milan, Italy, during the last decade. A minimum follow-up of six months was available on 496 patients. These patients received 560 treatments: 435 patients (87.7%) had a single treatment, 60 patients (12.1%) had two treatments, and one patient (0.2%) had five treatments (two on the right side, three on the left side). Twenty four patients had multiple sclerosis (4.8%). Four hundred and forty-three patients (84%) received the treatment without previous procedures, while 84 patients (16%) underwent radiosurgery after the failure of other treatments. A neurovascular conflict was identified in 59% of the patients. Three hundred and forty-three patients (receiving a total of 387 treatments) had a minimum of 36 months follow up. Pain relief rate at 6, 12, 18, 24, 30 and 36 months was respectively 92, 87, 87, 82, 78 and 76%. Forty-four patients out of 343 (12.8%) required a second treatment during the observed period. At 36 months post-treatment, 21 patients (6,1%) reported the presence of bothering facial hypoesthesia. Eighteen patients out of 21 (85.7%) developed this complication after a repeated treatment.ConclusionsFrameless image-guided robotic radiosurgery in experienced hands is a safe and effective procedure for the treatment of TN, providing excellent pain control rates in the absence of major neurological complications. Repeated treatments due to recurrent pain are associated with restored pain control but at the price of a higher rate of sensory complications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Microradiosurgical cortical transections generated by synchrotron radiation
No full textAbstractPurposeMicroplanar X-ray beams (microbeams) originated by synchrotron sources have been delivered to the visual brain cortex regions in rodents to create microscopically narrow lesions. The effects of microbeams mimic those generated by microsurgical subpial transections (also known as multiple subpial transections) but are obtained in a low-invasive way.MethodsImage-guided atlas-based microbeam cortical transections have been generated on seven 1 month-old Wistar rats. An array of 10 parallel beams of 25 microns in thickness and spaced of 200 micron center-to-center was centered on the visual cortex and deposited an incident dose of 600 Gy.ResultsThe procedure was well tolerated by rats. After recovery, rats showed regular behavior, no sign of gross visual impairment and regular weight gain. After 3 months, rats were sacrificed and brains histologically examined. Cortical transections resembling those obtained through a surgical incision were found over the irradiated region. Remarkable sparing of the cortical columns adjacent to the transections was observed. No sign of radionecrosis was evident at least at this time point.ConclusionsThe visual brain cortex transected by synchrotron-generated microbeams showed an incision-like path of neuronal loss while adjacent non irradiated columns remained intact. These preliminary findings, to be further investigated also using other techniques, suggest that microbeam radiosurgery can affect the cortex at a cellular level providing a potential novel and attractive tool to study cortical function
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